Waterborne polyurethane elastomers (WPUE), synthesized in aqueous solutions, represent a revolutionary sustainable alternative to thermoplastic polyurethane elastomers (TPUE), which are typically produced using organic solvent. This shift significantly reduces VOC emissions. However, WPUE often lacks the mechanical strength of TPUE produced through traditional synthetic methods, limiting its potential as a sustainable option. Here, we introduce a high-performance waterborne polyurethane elastomer that not only aligns with green chemistry principles but also achieves impressive toughness of 0.959GJ/m³ and strength of 81.8 MPa. This breakthrough is made possible by a self-reinforcement mechanism known as the delayed crystallization response, which arises from a dynamic biphase structure engineered with symmetrical monomers and hierarchical hydrogen bonds. During stretching, steric hindrance from hydrophilic segments delays crystallization until a stretch ratio of ~13, causing hard domains to fragment into isolated segments. Once the stretch ratio exceeds 20, co-crystallization occurs as hard and soft segments align, significantly enhancing both strength and toughness. This development offers a promising green and sustainable alternative to TPUE.